In the current networks, traffic of mobile terminals (smartphones or feature phones) occupies most of network resources. Furthermore, traffic used by mobile terminals tends to be continuously increased in the future.
In contrast, with the development of Internet of things (IoT) services (for example, transportation systems, smart meters, monitoring systems of devices or the like), there is a need to cope with services having various request conditions. Thus, in communication standards of 5G (fifth generation mobile unit communication), in addition to the technology of fourth generation mobile unit communication (4G), there is a demand for a technology that implements high-data-rate, high-capacity, and low-latency communication.
As described above, in 5G, in order to respond various kinds of services, support of a lot of use cases classified into eMBB (enhanced mobile broadband), Massive MTC (machine type communications), and URLLC (ultra-reliable and low latency communication) is conceived.
From among the use cases described above, URLLC is the most difficult use case to be implemented. First, there are demands of the error rate of 10−5 in a radio section, which is ultrahigh reliable communication. As a method of implementing ultrahigh reliability, there is a method for increasing an amount of resources to be used and providing redundancy to data. However, because an amount of radio resources is limited, it is not possible to increase the resources to be used without any limitation.
In addition, regarding a low latency, in URLLC, the aim of a delay in a radio section in a user plane in an uplink and a downlink is 0.5 milliseconds. This is a high request corresponding to less than 1/10 of 4G radio system Long Term Evolution (LTE). In URLLC, there is a need to simultaneously satisfy the above described two requests, i.e., ultrahigh reliability and low latency.
Furthermore, in 5G, there is a need to simultaneously support ultrahigh reliability and low latency communication data (URLLC data) and other data (for example, eMBB data, or the like) by using the same carrier, and thus, in order to implement this, it is desirable not to impair the efficiency of using frequency.
Some resource allocation methods for providing an URLLC service and another service (for example, an eMBB service, or the like) in a compatible manner have been proposed. As one of the proposed methods, there is an allocation method using a resource separation type that separates resources to be allocated to URLLC data from resources to be allocated to other pieces of data and reserves the resources regardless of whether URLLC data is present. In the allocation method using the resource separation type, because a data area used for the URLLC data is previously reserved, it is possible to always allocate a resource to the generated URLLC data. However, if there is no URLLC data to be transmitted, the resource that has been reserved for the URLLC data is not used; therefore, the efficiency of using the resource is degraded.
Furthermore, as another method, there is a proposed allocation method using a resource sharing type that shares the resources by the URLLC data and other pieces of data without separating the resources and transmitting, if URLLC data is generated, the URLLC data with priority by performing resource allocation for interrupting the URLLC data to the resource that has already been scheduled for another piece of data. In the resource sharing type, because a resource can be used for another piece of data in a case where URLLC data is not transmitted, the efficiency of using the resources is higher than that of the resource separation type.
Patent Document 1: Japanese Laid-open Patent Publication No. 2016-158304
Patent Document 2: Japanese Laid-open Patent Publication No. 2013-247513
Non-Patent Document 1: “New SID Proposal: Study on New Radio Access Technology”, NTT docomo, RP-160671, 3GPP TSG RAN Meeting #71, Goteborg, Sweden, 7th-10th Mar. 2016
Non-Patent Document 2: 3GPP TR 38.913 V0.3.0 (2016-03)
Non-Patent Document 3: “On co-existence of eMBB and URLLC”, NTT docomo, R1-167391, 3GPP TSG RAN WG1 Meeting #86, Gothenburg, Sweden, 22nd-26th Aug. 2016
Incidentally, in the resource sharing type, if URLLC data is generated, the URLLC data is transmitted by allowing the URLLC data to take higher a priority than the other piece of data and interrupt into a predetermined URLLC interruption resource area. Thus, in downlink communication in which a single base station device transmits both of the URLLC data and the other data, it is relatively easy to implement the allocation method using the resource sharing type.
However, in uplink communication in which each of a plurality of user terminal devices transmits the URLLC data and the other data, because a generation status of the URLLC data in another user terminal device is unknown, it is difficult to provide an URLLC interruption resource area. Namely, the user terminal device that transmits the other data does not recognize whether URLLC data is generated in another user terminal device, it is difficult to determine whether the other data is to be transmitted by using all of the resources or whether a part of resource needs to be left for the URLLC data that is transmitted by the other user terminal device.
Consequently, in uplink communication, the allocation method using the resource separation type that reserves the resources to be used to transmit the URLLC data regardless of whether URLLC data is generated is used and thus, the resources to be used to transmit the other data is decreased. As a result, there is a problem in which throughput of the other data is decreased. In contrast, in downlink communication that uses the resource sharing type, if URLLC data is generated, puncturing is performed on the other data that has been allocated to the resource interrupted by the URLLC data. Namely, because a part of the other data is lost in the URLLC interruption resource area, communication quality of the other data is decreased.